The present invention relates to a flexible intermediate bulk container (FIBC) having a double base construction and suitable for partial or complete discharge of bulk material.
An FIBC can be emptied either by using a long handled knife to cut one or more slits in the bottom or by lowering the FIBC onto a pyramidal shaped knife. These methods will destroy the base of the container and it cannot be reused. Further, by such method the entire contents of the FIBC will be discharged in a matter of seconds. This is not always desirable because the FIBC can contain 500-1500 kilos of bulk material. Partial discharge of bulk materials can, for various reasons, be desirable.
Norwegian patent No. 138,134 describes a FIBC with a double base construction. The FIBC comprises a sidewall structure with flaps which are integral extensions of the side wall fabric. Such flaps are joined two and two at their lower edges in such way that joining lines thereof cross at one point. Thus, the integral extensions of the pairs of equally large flaps form a double overlapping base.
Partial discharge of a FIBC will a single base construction and a discharge spout is a relatively simple operation. A great disadvantage related to this method is the need for working close to the base of a hanging container when the base mouth is opened or closed.
There has been developed a piece of board, for instance made of plastic material, to be used for partial discharge of a FIBC with a double base. This piece of board has a central opening and a handle at least at one end. The board is positioned between the flaps forming the double base. When the FIBC is emptied, a cut is made through the central part of the base. The bulk material flows freely out of the container when the opening in the board is positioned in the same position as the opening in the base of the container. The discharge is stopped and regulated by pulling or pushing the board away from the opening, and thus closing and opening in the base. In addition to the disadvantage of the necessity of working close to the base of a hanging container, this method also involves the disadvantage that the base is destroyed and the container is not reusable. A further disadvantage is that when the cut is performed some fabric from the base will pollute the bulk material. Also, the board has to be supplied separately to users, it cannot be an integral part of every container.